Post a character who often, always, 或者 almost always goes 由 his/her last name/surname

koichi sakakibara almost always goes 由 his last name,sakakibara...........

Zura! er... I mean Katsura X3 Kotarou Katsura, not once he was called 由 his first name in the anime, it's always Zura 或者 Katsura XD

i guess tetsuya kuroko always goes 由 the his last name kuroko

Kazahaya

Youhei Sunohara from CLANNAD. The only character who ever really addressed him as 'Youhei' was Kyou Fujibayashi, and he had not granted her permission 或者 clarified that he felt comfortable with that.